1988 Burban TBI throwing 42 code

[Kevro_N_Chevro]

I have been going through this rig replacing any and all parts. Got all the sensors I could from rockauto. I will need to refer to the receipt to double check them all. New distributor plugs msr wires. New cam then still would get a 42 code it would run !ike scrap. You can shut off the key, restart it and its fine for a while. It will also die at random. Then take a few seconds to restart. So I replaced the icm thinking it might have burned out. I have a mechanic that has instructed me to tale two of the four icm plug wires and connect them with a bit connector. He can't remember which two says he thinks A.and D. This will block the ecm from.advancing the timing. Anyone have any issues like this?

 

[Blackbeard44]

i would be looking for a broken wire somewhere, just my guess, It's been a long time since I have owned a TBI motor.

only issues I ever had was Ignition Modules, Coolant Temp Sensor, and Throttle Position Sensor

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[Chevyguy]

I have been going through this rig replacing any and all parts. Got all the sensors I could from rockauto. I will need to refer to the receipt to double check them all. New distributor plugs msr wires. New cam then still would get a 42 code it would run !ike scrap. You can shut off the key, restart it and its fine for a while. It will also die at random. Then take a few seconds to restart. So I replaced the icm thinking it might have burned out. I have a mechanic that has instructed me to tale two of the four icm plug wires and connect them with a bit connector. He can't remember which two says he thinks A.and D. This will block the ecm from.advancing the timing. Anyone have any issues like this?

Check your base timing with the EST unplugged to verify it is set to zero degree's. Turn off the engine then reconnect the EST connection. Make sure you do this with the engine warmed up. Recheck your timing, normally ecm will advance the timing 15 degree's. If the 42 code still shows disconnect the battery ground cable for 15 seconds to clear it. I would disregard what the mechanic said to do because you might end up shorting out the ECM.

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[Mango]

Having the same issues just starting to do research HELP!

 

[squaredeal91]

Try unplugging coolant temperature sensor and try starting it then to see if it acts any different.

 

[BurbanPena]

on the left hand side above the valve cover there is a black box it’s your ignition control module there two wires that are crimped together on one ring terminal that are grounded to the intake manifold if they are hard to the touch and have lumps in the wires they need to be replaced you can cut the wire back as far as you can until you get to a cleaner peace of wire and solder or crimp new wire and install a new ring terminal

 

[Ricko1966]

What your mechanic said to do was a common est bypass that lots of people did I don't recommend it. But your burb shouldn't have that distributor anyway so that is irrelevant. Code 42 is a circuit malfunction,a broken wire,a grounded wire a shorted component or an ecm trying to fail,double and triple check all est and ignition primary wires. Then start testing individual components. A shortcut on checking continuity from ecm to individual components is. Disconnect the battery ,disconnect the ecm plug ,find your wire in question at the ecm plug,jumper wire it to ground,same wire,under hood end Disconnect it, check for continuity to ground. No continuity, then that wire is open.Got continuity,Disconnect your jumper at the ecm. No continuity your wire is good. Still have continuity? Your wire is shorted.

 

[gmbellew]

check the drivability and emissions manual. of the 4 wires leaving the ignition control module, only 1 or maybe 2 of them will set code 42 if there is an issue. usually it is the EST wire itself, which, when disconnected, runs the engine only on the base timing built into the ignition control module. which would explain why it runs like crap. that wire is black and tan. i'd suggest making sure the connector at the ignition control module is good on that wire and the in-line plug near the brake booster is good. if so, checking continuity on the wires or doing some of the checks in the manual to narrow it down would be what I would do.

 

[gmbellew]

adding info to an old thread to consolidate for future searches.

I had a code 42 popping on me randomly and intermittently. I could feel the engine skip when it would happen and 1 time it died at a stop light. 1 time on a long higheay run the light went off on its own when the engine skipped again. but usually required a restart to clear.

I know code 42 is usually only set with issues on the EST (white wire) or bypass (tan and black wite). because I lost my low reference (ground red and black wire) and it gave me extra reference pulses but it never set a code 42.

some other things were going haywire also, like Open Loop when it should be closed and some weird TCC lockup. given the variety of issues, and the complete tuneup I had given it 1 month ago. so I thought maybe the ECM was going bad. swapped in my spare, and same issue.

all the ECM and ICM wires and connections seemed good, and I am always careful to route plug wires away from the ECM wires.

finally decided maybe the ICM was going out intermittently. took off the 1 month old distributor cap to swap in my spare ICM and saw the cap cracked in 3 places with obvious carbon tracking from voltage leaving the cap. I presume it was arcing over and putting voltage on the EST or bypass wires to throw the code 42 and bouncing off who knows what to give the other issues. been 3 days with the new cap and so far so good. hope this helps somebody.